Little is known about the interactions of the parasympathetic and sympathetic nerves in the developing heart. This application proposes to study these interactions by selectively removing the parasympathetic and/or sympathetic nerves to the chick embryonic heart. Since the peripheral ganglia of the autonomic systems derive from specific areas of neural crest, the lesions will be accomplished by selectively removing those areas of neural crest which contribute autonomic nerves to the heart. The hearts and remaining innervation will then be evaluated by a variety of chemical, morphological and physiological techniques. Following various combinations of neural crest extirpations horseradish peroxidase will be injected and the origin of the remaining nerves will be mapped. Catecholamines and catecholamine uptake will be measured in denervated hearts and correlated with fluorescence histochemistry. Cholinergic muscarinic receptors will be measured in denervated and control hearts using 3H-quinuclidinyl benzylate and adrenergic beta-receptors will be measured using 3H-dihydroalprenolol. Histochemical methods will be applied to determine changes in enzyme levels in cardiac muscle and the conducting system of the denervated hearts at various stages of development after the different lesions. Electrocardiograms will be obtained daily throughout incubation in all the lesioned and control groups to determine changes in heart rate and conduction potentials and sensitivity of denervated hearts to different drugs. These studies should provide basic information about the influence exerted by the two autonomic systems on each other during development and their influence on end organ development and function.